In order to properly contain and process contaminant materials, it is necessary to understand not only what materials are being dealt with, but also the quantity of a contaminant in a particular location. As such, a variety of testing protocols and materials have been developed to identify and quantify compounds in waste facilities, storage facilities, ground water, etc. For instance, separation media including adsorbents, absorbents, and ion exchange media have been developed to identify and quantify contaminants that may be present in an area. To accurately identify and quantify any particular contaminant, however, it is necessary to know the affinity of that contaminant for a particular separation medium. Thus, the separation medium must itself be examined before it is possible to use with a high level of confidence.
In a typical method for determining the affinity of a species for a separation medium, an aliquot of a mixture that includes the species is separated and analyzed to determine the concentration of the species, and the remainder of the mixture is placed in contact with a separation medium, e.g., an ion exchange medium. Following a period of contact between the mixture and the separation medium, the solution and solid phases are separated by filtration, centrifugation, etc., and the solution is analyzed by an appropriate technique to determine the remaining concentration of the species. The difference between the initial concentration and that measured after some time interval is that assumed to have sorbed/exchanged onto the solid phase. Analysis of the solids, when pursued, requires additional handling prior to analysis. For instance, interstitial liquid must be removed by rinsing with an inert solution, the solids dried to constant weight and dissolved for analysis. The additional sample handling introduces additional experimental uncertainty and error. Furthermore, by taking aliquots from a test reaction composition, the phase ratio of liquid to solids may be inadvertently changed by an unknown amount if the sampling event does not remove a homogeneous aliquot. These methods are laborious and operationally complex, which can lead to error in accurate characterization of the media.
In view of the above, what is needed in the art is a simple, efficient, and reproducible method of determining the affinity of targeted species for separation media. For instance, a method for determining the distribution coefficient of a species for an ion exchange or sorbent medium that is faster and less expensive than current methods and that prevents errors as may come from excessive sampling and handling would be of great benefit.